JP2009-108778A discloses a fuel injection device which causes fuel to swirl and diffuse in a swirl flow to form a stratified mixture gas. Specifically, an auxiliary injection in which a small amount of fuel is injected is performed in a final stage of compression stroke. By causing the fuel to swirl and diffuse in the swirl flow, the stratified mixture gas is formed around a spark plug, and the stratified mixture gas is ignited to cause a fire. During or after combustion of this mixture gas, a main injection of fuel is performed. Thus, compression ignition reliably occurs.
However, if a temperature of an external environment is low, since the temperature of the engine drops, a temperature inside a combustion chamber accordingly drops. In a case of performing SI combustion, if the temperature inside the combustion chamber is low, spark ignition becomes difficult. If the stability of the SI combustion degrades, flame propagation slows down, which also degrades stability of CI combustion. If the flame propagation slows down, rich mixture gas and lean mixture gas may not be distributed suitably inside the combustion chamber at an ignition timing, and a reduction in NOx generation or an improvement in fuel efficiency cannot be achieved.